The present invention relates to a controller of a clinker cooler used for cement production such as a cement clinker.
Heretofore, in devices for burning raw meal of cement such as cement clinker, an air quenching cooler (heretofore referred to as "a cooler") has been used in the quick cooling of red-hot clinker burnt in a rotary kiln through thermal exchange with cooling air blown from below an oscillating grate upon which the clinker is moved, the cooling air is heated through the thermal exchanged with the high temperature clinker in the cooler and it is partly used as combustion air of a kiln and a furnace in the preheater, with the excessive air being exhausted out of the cooler.
As such a cooler, that is cooler 2 as shown in FIG. 2, is in general a grate type air quenching cooler for cooling a clinker 10 by dropping a red-hot clinker 10 on a lattice-like grate 3, blowing air by fans 14, 15, 16 and 17 from the lower portion of the perforated plate 3 while moving the clinker 10 by reciprocating the grate 3. In such a grate type air quenching cooler, the cooling air which has been thermally exchanged with the red-hot clinker 10 is thermally recovered as the secondary air for the kiln and the burning furnace in the preheater, and the excessive air is exhausted out of the cooler by an exhaust fan 22.
Further, as a method of introducing stabilized kiln secondary air, in such a clinker cooler device, a method of operating the rotating speed of the cooler exhaust fan or the opening of a damper 23 has been previously adapted to make the pressure of a hood 11 in the outlet of the kiln constant.
However, the abovementioned method of controlling the clinker cooler has the following disadvantages. The pressure in the kiln outlet hood 11 varies in accordance with the variation in the rotating speed of the kiln exhaust gas fan, the variation in the ventilating resistance resulting from the variations in the coating of raw material in side the kiln 1 and/or the variations in the secondary air temperature of the kiln. When the rotating speed of the cooler exhaust fan 22 or the opening of the damper 23 are varied so as to maintain the pressure constant in the hood 11, the quantity of the air exhausted from the cooler 2 changes in response to the above mentioned. Since the total quantity of the clinker cooling air thus introduced into the cooler 2 is maintained at a constant value and the secondary air for the furnace in the preheater is also controlled to be a constant value, the variation in the amount of air thus exhausted from the cooler 2 is relative to the variation in the quantity of the secondary air of the kiln.
Recently, as a baffle plate 13 has been hung over the clinker layer in the cooler 1, in order to stabilize the introduction of the secondary air for the kiln and the furnace in preheater and to reduce the radiation heat loss from the red-hot clinker 10, the ventilating resistance over the clinker layer increases causing a decrease in the response velocity in variations in the rotating speed of the cooler exhaust fan 22 and in variations in the pressure of the hood 11 at the outlet of the kiln 1 with respect to the variations in the opening of the fan damper 23. Therefore, the amount of variation in the cooler exhaust air increases or an alteration in the quantity of the secondary air of the kiln increases. Consequently, there are not only such disadvantages that the burning state of fuel in the kiln 1 changes and the quality of the clinker to be burnt is decreased, but the fuel consumption of the system also increases.